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Chris A. Martini, Dewayne L. Ingram, and Terril A. Nell

Growth of Magnolia grandiflora Hort. `St. Mary' (southern magnolia) trees in containers spaced 120 cm on center was studied for 2 years. During the 1st year, trees were grown in container volumes of 10, 27, or 57 liter. At the start of the second growing season, trees were transplanted according to six container shifting treatments [10-liter containers (LC) both years, 10 to 27LC, 10 to 57LC, 27LC both years, 27 to 57LC, or 57LC both years]. The mean maximum temperature at the center location was 4.8 and 6.3C lower for the 57LC than for the 27 and 10LC, respectively. Height and caliper, measured at the end of 2 years, were” greatest for magnolias grown continuously in 27 or 57LC. Caliper was greater for trees shifted from 10LC to the larger containers compared with trees grown in 10LC both years. Trees grown in 10LC both years tended to have fewer roots growing in tbe outer 4 cm of the growing medium at the eastern, southern, and western exposures. During June and August of the 2nd year, high air and growth medium temperatures may have been limiting factors to carbon assimilation. Maintenance of adequate carbon assimilation fluxes and tree growth, when container walls are exposed to solar radiation, may require increasing the container volume. This procedure may be more important when daily maximum air temperatures are lower during late spring or early fall than in midsummer, because low solar angles insolate part of the container surface.

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Lori A. Black, Terril A. Nell, and James E. Barrett

Dormant-budded `Gloria' azaleas (Rhododendron sp.) at various maturity levels (one, eight, or 32 individual open flowers) were moved from the greenhouse to postproduction rooms. Postproduction rooms were maintained at 21 ± 1C, relative humidity 50% ± 5%, and 12 hours of daily irradiance at 12 μmol·s–1·m–2 from cool-white fluorescent lamps to simulate home conditions. Using predetermined categories, the number of tight, showing-color, candle, and open-flower inflorescences were recorded. After 2 weeks postproduction, plants chosen at the start of postproduction with eight or 32 individual open flowers had the best flowering uniformity and flower color. In a second experiment, azaleas with one, eight, or 32 individual open flowers were placed into simulated transport for 4 days at 16 ± 1C. Plants with one individual open flower had greatest longevity, but those with eight open flowers had the best overall postproduction performance. In a final experiment, azaleas at similar maturity levels were placed in simulated transport at 5, 16, or 27C for 2, 4, or 6 days. After 2 weeks postprodudion, there was no difference due to simulated-transport temperature or duration on flowering performance or flower color. Longevity was good for plants held 2, 4, or 6 days at 5C and for plants held for 2 days at 16 or 27C.

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Barbara C. Poole, Terril A. Nell, and James E. Barrett

Premature flower bud abscission imposes a serious limitation on longevity of potted Hibiscus in interiorscape situations, Ethylene is known to be one causative factor. Past research has suggested that carbohydrate depletion of buds may also be involved,

A series of experiments was conducted to examine the relationship between carbohydrate levels and ethylene sensitivity of flower buds under low irradiance levels. Two cultivars were used: `Pink Versicolor', which is very susceptible to bud abscission, and the more resistant `Vista', In the first experiment, plants were harvested twice weekly after placement in interiorscape rooms (8.5 μmol m-2 s-1 for 12 hrs per day; 26.5°C day/night) until all buds had abscissed. At each harvest, buds from four size groups were collected for analysis. In the second experiment, source/sink strength of buds was manipulated by selective daily removal of certain sized buds. Remaining buds were collected just prior to abscission for analysis. In two additional experiments, `Pink Versicolor' plants were treated with either silver thiosulfate or ethephon prior to placement in interiorscape rooms. Plants were harvested twice weekly and buds collected. For all experiments, bud dry wt, total soluble sugars and starch content were determined.

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William M. Womack, Terril A. Nell, and James E. Barrett

Dormant-budded `Prize' azaleas (Rhododendron sp.) were held at 2C, 7C, 13C, or 18C for 1, 2, 4, 6, 8, or 10 weeks then forced in walk-in growth chambers (29C day/24C night). Holding at 2C delayed flowering by 5-7 days over 7C and 13C. Plants held at 2C, 7C, or 13C for at least 4 weeks had approximately 50% buds showing color at marketability (8 open flowers). Plants held at 18C never exceeded 35% buds showing color at marketability. Increase in buds showing color was not apparent for plants were held at 7C, 13C, or 18C for more than 6 weeks; however, holding at 2C resulted in increasing percentages of buds showing color for holding periods longer than 6 weeks. Plants chilled at 13C and 18C showed significant increases in bud abortion after 8 or 10 weeks of cooling with most plants never reaching marketability (8 open flowers). These plants also had an increased proliferation of bypass shoots during cooling and forcing over other treatments.

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Andrew J. Macnish, Ria T. Leonard, and Terril A. Nell

The postharvest longevity of fresh-cut flowers is often limited by the accumulation of bacteria in vase water and flower stems. Aqueous chlorine dioxide is a strong biocide with potential application for sanitizing cut flower solutions. We evaluated the potential of chlorine dioxide to prevent the build-up of bacteria in vase water and extend the longevity of cut Matthiola incana `Ruby Red', Gypsophila paniculata `Crystal' and Gerbera jamesonii `Monarch' flowers. Fresh-cut flower stems were placed into sterile vases containing deionized water and either 0.0 or 2 μL·L–1 chlorine dioxide. Flower vase life was then judged at 21 ± 0.5 °C and 40% to 60% relative humidity. Inclusion of 2 μL·L–1 chlorine dioxide in vase water extended the longevity of Matthiola, Gypsophila and Gerbera flowers by 2.2, 3.5, and 3.4 days, respectively, relative to control flowers (i.e., 0 μL·L–1). Treatment with 2 μL·L–1 chlorine dioxide reduced the build-up of aerobic bacteria in vase water for 6 to 9 days of vase life. For example, addition of 2 μL·L–1 chlorine dioxide to Gerbera vase water reduced the number of bacteria that grew by 2.4- to 2.8-fold, as compared to control flower water. These results confirm the practical value of chlorine dioxide treatments to reduce the accumulation of bacteria in vase water and extend the display life of cut flowers.

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Robert H. Stamps, Terril A. Nell, and James E. Barrett

Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] fronds produced under a high-temperature regime (HTR, 30 day/25C night) grew faster and produced sori earlier than those in a low-temperature regime (LTR, 20 day/15C night). Abaxial diffusive conductance was lower for HTR-grown fronds. Light-saturated net CO2 assimilation rates (Pn) and dark respiration were lower for HTR fronds, but light-saturated Pn efficiencies (chlorophyll basis); light compensation points; and soluble sugars, starch, and nonstructural carbohydrate levels were similar for the two regimes. Transpiration and water-use efficiency (mass basis) at light saturation were similar for fronds from both temperature treatments. Comparison of physiological characteristics of fronds from the two temperature regimes revealed no differences that might account for reduced postharvest longevity of fronds produced at the higher temperatures.

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Nadia Roude, Terril A. Nell, and James E. Barrett

Chrysanthemums `Bright Golden Anne' and `Iridon' [Dendranthemum ×grandiflorum (Ramat.) Kitamura] were grown with N concentrations of 1.3, 2.6, or 5.2 kg N/m' of water during the crop cycle from either Osmocote slow-release 14N-6.2P-11.6K or 12.4N4.4P-14.lK or Peters soluble 20N-4.4P-16.6K. Plants were moved to simulated interior rooms at flowering to evaluate effects of the treatments on longevity. `Bright Golden Anne' longevity was not affected by fertilizer source, but `Iridon' longevity was reduced when Peters soluble fertilizer was applied at 2.6 and 5.2 kg N/m3 of water, whereas N concentration did not affect longevity when the slow-release Osmocote fertilizer was used. In an additional study, `Tip', `Copper Hostess', and `Iridon' were grown in three soil media using 1.3, 2.6, or 5.2 kg N/m' of water using Peters soluble 20N-4.4P-16.6K fertilizer from time of planting until flowering. Longevity increased as N concentration decreased when chrysanthemums were grown in Metro Mix 350, whereas N concentration had no significant effect on chrysanthemums grown in Vergro Klay Mix or a peat-perlite-sand mix. `Tip' showed significant in. creases in longevity as N concentration decreased.

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Richard Kent Schoellhorn, James E. Barrett, and Terril A. Nell

Treatments were cultivar, uniconazole concentrations (0, 2, 4, or 8ppm), and time between dip and placement under mist (0, 10, or 60 minutes). Unrooted chrysanthemum cuttings of cultivars `Tara' and `Boaldi' were dipped in uniconazole solutions for 10 seconds. Data were taken 16 days after treatment. A quadratic relationship was found for the interaction between concentration and cultivar. `Tara': (y = 6.7277-1.532(x) + 0.119409(x2)) and `Boaldi': (y= 6.4676-0.884(x)+0.060020(x 2). Time had no significant interaction with either cultivar or uniconazole concentration.

In a second study, with uniconazole concentrations and storage time (10 minutes or 12 hours), main effects and the cultivar concentration interaction were significant.

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Brent M. Chapman, James E. Barrett, and Terril A. Nell

Catharanthus roseus `Cooler Peppermint' were grown under four different watering regimes [well-watered (WW), wilt plus 1 day (W+1), wilt plus 3 days (W+3), and wilt plus 1 day during the last 2 weeks only (L W+1)] and two different light levels [1100 and 750 μmol·m–2·s–1]. Stress treatments affected finished plant size and leaf area as well as stomatal conductance, water potential and time to wilt during two dry-down periods imposed at the end of an 8-week production cycle. W+3 plants were 50% smaller with 50% less leaf area compared to WW plants. During the second dry-down period, WW plants in high light wilted in 2 days vs 4 days for the W+3 plants. Similarly, WW plants in low light wilted in 3 days vs 6 days for the W+3 plants. The W+3 plants maintained significantly higher water potentials and greater stomatal conductances than the other treatments throughout both dry-down periods.

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Andrew J. Macnish, Ria T. Leonard, and Terril A. Nell

Exposure to 0.1, 1.0, or 10 μL·L−1 ethylene for 4 days at 21 °C reduced the display life of 17 commonly traded potted foliage plant genotypes (Aglaonema ‘Mary Ann’, Anthurium scherzerianum ‘Red Hot’ and ‘White Gemini’, Aphelandra squarrosa ‘Dania’, Chlorophytum comosum ‘Hawaiian’, Codiaeum variegatum pictum ‘Petra’, Dieffenbachia maculata ‘Carina’, Dracaena marginata ‘Bicolor’ and ‘Magenta’, Euphorbia milii ‘Gaia’, Euphorbia splendens ‘Short and Sweet’, Ficus benjamina, Polyscias fruticosa ‘Castor’, Radermachera sinica ‘China Doll’, Schefflera elegantissima ‘Gemini’, Schefflera arboricola ‘Gold Capella’, Spathiphyllum ‘Ty's Pride’). Ethylene treatment hastened leaf and bract abscission or senescence. The responsiveness of plants to ethylene varied considerably; six genotypes were sensitive to 0.1 μL·L−1 ethylene, whereas three genotypes required exposure to 10 μL·L−1 ethylene to trigger visible injury. Four genotypes (Asplenium nidus, Chamaedorea elegans ‘Neathe Bella’, Hedera helix ‘Chicago’, Syngonium podophyllum ‘White Butterfly’) included in our study were insensitive to ethylene. Treating Aglaonema ‘Mary Ann’, Polyscias fruticosa ‘Castor’, and Schefflera arboricola ‘Gold Capella’ plants with 0.9 μL·L−1 1-methylcyclopropene (1-MCP, provided as EthylBloc™), a gaseous ethylene-binding inhibitor, for 4 to 5 h at 21 °C reduced the deleterious effects of ethylene. The release of 1-MCP from two sachets containing EthylBloc™ into a single shipping box also protected Aphelandra squarrosa ‘Dania’, Euphorbia milii ‘Gaia’, Polyscias fruticosa ‘Elegans’, and Schefflera arboricola ‘Gold Capella’ plants from ethylene injury after simulated transport. Our data reveal the genetic variation in ethylene sensitivity among potted foliage plants and highlight genotypes that benefit from 1-MCP treatment.